JP5010436B2 - Liquid developer - Google Patents

Description

The present invention relates to a liquid developer for electrophotography or electrostatic recording used in printing machines, copying machines, printers, facsimiles and the like.

As the liquid developer, generally, a developer in which colored resin particles (hereinafter, also referred to as toner particles) containing a colorant such as a pigment are dispersed in an electrically insulating medium is used. In the present invention, a coacervation method which is one of methods for producing such a liquid developer will be described. The coacervation method is a method for coloring a resin contained in a mixed state by removing the solvent from a mixed solution of a solvent that dissolves the resin and an electrically insulating medium that does not dissolve the resin. In this method, the resin is deposited so as to enclose the agent to form colored resin particles, and the colored resin particles are further dispersed in an electrically insulating medium.

The liquid developer obtained by such a method is considered to have better electrophoretic properties because the colored resin particles have a shape close to a sphere and a uniform particle size than the liquid developer obtained by the wet pulverization method. Yes.
However, an image obtained by printing using a liquid developer obtained by the coacervation method generally has a problem of low friction resistance.

Conventionally, as a method for improving the friction resistance of a liquid developer, although not a coacervation method, a method of adding a wax (for example, refer to the column of the prior art in Patent Document 1), toner particles having a specific melting temperature A method (for example, see Patent Document 2) in which a constituent resin and an additive material (polyethylene wax or the like) are used in combination has been proposed.

Therefore, in order to improve the abrasion resistance of the liquid developer obtained by the coacervation method, it is conceivable to contain the proposed polyethylene wax or the like, but even if such polyethylene wax or the like is contained, The abrasion resistance of the obtained image is not improved and is insufficient, and has a particular problem in the production by the coacervation method.
JP 60-098446 A Japanese National Patent Publication No. 10-510063

Therefore, the present invention provides good wear resistance in a liquid developer for electrophotography or electrostatic recording, particularly in a liquid developer for electrophotography or electrostatic recording obtained by using a coacervation method. It is an object of the present invention to provide a liquid developer.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that at least two colored resin particles comprising a pigment and a binder resin, an insulating hydrocarbon-based organic solvent that does not dissolve the binder resin, and the insulating properties described above. A liquid developer containing a dispersant dissolved in a hydrocarbon-based organic solvent and a liquid developer containing a charge control agent, and further containing oxidized polyethylene wax treated in the presence of a compound having a basic group It has been found that the wear resistance of the obtained printed matter is improved by using it, and the present invention has been completed.

That is, the present invention is (1) colored resin particles composed of at least two components of a pigment and a binder resin, an insulating hydrocarbon organic solvent (solvent (b)) that does not dissolve the binder resin, and dissolved in the solvent (b). The present invention relates to a liquid developer characterized by containing a dispersant (dispersant (A)), an oxidized polyethylene wax treated in the presence of a compound having a basic group, and a charge control agent.
The present invention also provides (2) colored resin particles comprising three components of at least a pigment, a solvent (b) insoluble or sparingly soluble dispersant (dispersant (B)), and a binder resin, solvent (b), and dispersant. (A), and a liquid developer containing a charge control agent and obtained by using a coacervation method, and further, oxidized polyethylene wax in the solvent (b) in the presence of a compound having a basic group. The present invention relates to the liquid developer described in the above item (1), in which the dispersed oxidized polyethylene wax dispersion is blended.
Further, the present invention includes (3) a colored resin particle composed of at least two components of a pigment and a binder resin, a solvent (b), a dispersant (A), and a charge control agent, and utilizes a wet pulverization method. The liquid developer as described in (1) above, wherein the obtained liquid developer is further blended with an oxidized polyethylene wax dispersion in which an oxidized polyethylene wax is dispersed in a solvent (b) in the presence of a compound having a basic group. It relates to the agent.
The present invention also includes (4) a pigment, a binder resin, a solvent that dissolves the binder resin (solvent (a)), a solvent that does not dissolve the binder resin and has a lower SP value than the solvent (a) ( b) Dispersant (A) that dissolves in both of the solvents (a) and (b), Dispersant (B) that dissolves in the solvent (a) and is insoluble or sparingly soluble in the solvent (b) And a coacervation method in which the solvent (a) is distilled off from the mixed liquid containing the oxidized polyethylene wax to precipitate the binder resin and the dispersant (B) in a dissolved state. A liquid developer comprising a dispersion obtained by adding a charge control agent, wherein the dispersant (A) and / or (B) is a dispersant having a basic group. The present invention relates to a liquid developer.
The present invention also includes (5) a colored chip obtained by heating and kneading a pigment and a binder resin, containing a dispersant having a basic group as the dispersant (A), an oxidized polyethylene wax, and a solvent (b). Dispersed in a mixture and colored chips obtained by heating and kneading a pigment mixed with a charge control agent and a binder resin into a dispersion obtained by using a wet pulverization method, a basic group as a dispersant (A) The dispersion according to (1) above, wherein the dispersion liquid and the oxidized polyethylene wax are dispersed in a solvent (b) using a wet pulverization method, and the resulting dispersion is blended with a charge control agent. The present invention relates to a liquid developer.
Moreover, this invention is described in any one of the above items (1) to (3), wherein (6) the compound having a basic group is a reaction product of a polyamine compound and a 12-hydroxystearic acid self-condensate. The present invention relates to a liquid developer.
The present invention also relates to (7) the liquid developer according to any one of (1) to (6) above, wherein the charge control agent is a salicylic acid metal salt.

Hereinafter, the liquid developer of the present invention will be described in detail.
Colored resin particles comprising at least two components of a pigment and a binder resin that are the liquid developer of the present invention, an insulating hydrocarbon organic solvent (solvent (b)) that does not dissolve the binder resin, and a dispersant (dissolvable in the solvent ( Dispersant (A)), oxidized polyethylene wax treated in the presence of a compound having a basic group, and a liquid developer containing a charge control agent can be obtained by various production methods. A liquid developer obtained by using a typical coacervation method and a wet pulverization method from which the above liquid developer can be obtained will be specifically described.

<Liquid developer obtained using coacervation method>
(Constituent materials)
As pigments to be used, inorganic pigments and organic pigments can be used. Inorganic pigments such as acetylene black, graphite, bengara, yellow lead, ultramarine blue, carbon black, azo pigments, lake pigments, phthalocyanine pigments, isoindoline pigments, anthraquinone pigments Organic pigments such as quinacridone pigments are preferred.
The content of these pigments is not particularly limited, but is preferably 2 to 20% by mass in the final liquid developer from the viewpoint of image density.

Next, as the binder resin to be used, a known binder resin (resin that dissolves in the solvent (a) described later and does not dissolve in the solvent (b) described later) that has been conventionally used in liquid developers can be used. For example, resins such as epoxy resins, acrylic resins, ester resins, alkyd resins, and rosin-modified resins can be used, and these resins can be used alone or in combination of two or more.

Next, as a solvent used in the coacervation method, a solvent (solvent (a)) that dissolves the binder resin and an insulating material that does not dissolve the binder resin and has a lower SP value than the solvent (a). Two kinds of organic hydrocarbon-based organic solvents (solvent (b)) are used in combination.

Specifically, the solvent (solvent (a)) for dissolving the binder resin preferably has an SP value of 8.5 or more, ethers such as tetrahydrofuran, ketones such as methyl ethyl ketone and cyclohexanone, ethyl acetate and the like. If the resin has a dissolving ability, aromatic hydrocarbons such as toluene and benzene may be used. These may be used alone or in combination of two or more.

On the other hand, as the insulating hydrocarbon-based organic solvent (solvent (b)), hydrocarbons that do not dissolve the binder resin, have electrical insulation, and have a lower SP value than the solvent (a) are used. it can. The SP value of the solvent (b) is preferably less than 8.5.

Specific examples include aliphatic hydrocarbons and alicyclic hydrocarbons, and may be aromatic hydrocarbons or halogenated hydrocarbons as long as the binder resin is not dissolved. Among these, a normal paraffin solvent, an isoparaffin solvent, and a cycloparaffin solvent are preferable from the viewpoint of odor, harmlessness, and cost. Examples of commercially available products include Isopar G, Isopar H, Isopar L, Isopar M, Exol D130, Exol D140 (all of which are manufactured by Exxon Chemical Co., Ltd.), Shellsol 71 (manufactured by Shell Petrochemical Co., Ltd.), IP Solvent 1620, IP Solvent 2080, IP Solvent 2835 (all manufactured by Idemitsu Petrochemical Co., Ltd.), Moresco White P-40, Moresco White P-55, Moresco White P-80 (all of which are Matsumura Oil Research) ), Liquid paraffin No. 40-S, liquid paraffin No. 55-S (all of which are manufactured by Chuo Kasei Co., Ltd.) and the like are preferable.

In addition, in this invention, SP value (solubility parameter) of a solvent is a value represented by the square root of molecular aggregation energy, and uses the value as described in Polymer HandBook (Second Edition) Chapter IV Solubility Parameter Values. The unit is (MPa) ^1/2 and indicates a value at 25 ° C. In addition, R.D. F. It can be calculated by the method described in Fedors, Polymer Engineering Science, 14, p147 (1967).

Next, as the dispersant used in the coacervation method, the dispersant (A) that dissolves in both the solvent (a) and the insulating hydrocarbon solvent (b), and the solvent (a) Is dissolved, but two types of the insoluble or hardly soluble dispersant (B) are used in combination in the insulating hydrocarbon solvent (b).

In the present invention, the dispersant (A) is dissolved in the solvent (a) and the solvent (b), the dispersant (B) is dissolved in the solvent (a), and is insoluble or hardly soluble in the solvent (b). As an index, the solubility of the dispersant (A) or the dispersant (B) in the solvent (a) or the solvent (b) can be used. In the present invention, when the solubility of the dispersant (A) in the solvent (a) and the solvent (b) is 1.0 g / 100 g (solvents (a) and (b)) or more at 25 ° C. When the solubility of the dispersant (B) in the solvent (a) is 1.0 g / 100 g (solvent (a)) or more at 25 ° C., the solubility of the dispersant (B) in the solvent (b) is 25 ° C. And less than 1.0 g / 100 g (solvent (b)) is regarded as insoluble or hardly soluble. Here, the solubility is a value obtained by filtering the solution dissolved up to the solubility limit and then measuring the solid content of the filtrate by a gravimetric method.
For the binder resin, the meanings of “dissolve the binder resin” and “do not dissolve the binder resin” are the same.

As such a dispersant, a known dispersant can be used, and the combination of the dispersant (A) and the dispersant (B) is not particularly limited as long as each condition is satisfied. However, depending on the solvent used, even if the same dispersant is used, the condition (A), the condition (B), or the case that does not correspond to either condition may be different. Therefore, when the solvent (a) and the insulating hydrocarbon solvent (b) are determined, the conditions for the dispersant (A) are satisfied in a preliminary test, and the conditions for the dispersant (B) are satisfied. It is preferable to classify them and select a combination from the respective classifications as appropriate.

Incidentally, the candidates for the dispersant (A) or the dispersant (B) are specifically anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, silicon Surfactants such as surfactants, fluorosurfactants and derivatives thereof, polyurethane resins, modified novolak resins having a ring-opening structure of epoxy groups with carboxyl groups derived from aromatic rings and hydroxycarboxylic acids, and / or graft copolymers Polymer (Japanese Unexamined Patent Publication No. 9-302259), poly (hydroxycarboxylic acid ester), a dispersant having a polar group such as a base at its terminal, and polyester introduced into the amino group and / or imino group of the (poly) amine compound Carbodiimide compounds having a modified (poly) amine derivative, polyester side chain, polyether side chain or polyacryl side chain International Publication WO 03/07652), a carbodiimide compound having a basic nitrogen-containing group and a polyester side chain, polyether side chain or polyacryl side chain in the side chain (International Publication WO 04/000950), pigment adsorbing part And a polymer type pigment dispersion resin such as a carbodiimide compound having a side chain having a colorant (International Publication WO04 / 003085). As what is marketed, for example, BYK-160, 162, 164, 182 (manufactured by Big Chemie), EFKA-47, 4050 (manufactured by EFKA), Solspers 17000, 24000 (manufactured by Geneca), Ajisper PB-817 821 (manufactured by Ajinomoto Co., Inc.). The dispersants (A) and (B) may be used alone or in combination of two or more.

Furthermore, the optimal use amount ratio (mixing ratio) of the dispersant (A) and the dispersant (B) may vary depending on the combination with the solvent in addition to the performance of each dispersant itself. The mass ratio of dispersant (A): dispersant (B) is preferably about 99: 1 to 1:99, more preferably 95: 5 to 5:95. The total amount of the dispersants (A) and (B) used (total amount) is preferably 0.1 to 200 parts by weight, more preferably 100 parts by weight of the pigment in the liquid developer of the present invention. Is 10 to 100 parts by mass.

The total blending amount of the dispersant (B), the pigment and the binder resin that are insoluble or hardly soluble in the insulating hydrocarbon solvent (b) contained in the liquid developer obtained by using the coacervation method is as follows: 10 to 50% by mass, and more preferably 15 to 40% by mass. When the amount is less than 10% by mass, a high-concentration product cannot be obtained.

Next, as the oxidized polyethylene wax treated in the presence of the compound having a basic group, the oxidized polyethylene wax and the compound having a basic group are stirred and mixed in the insulating hydrocarbon solvent (b). Use the same thing.
The mixture that has been stirred and mixed may be a mixture in which an oxidized polyethylene wax and a compound having a basic group are previously stirred and mixed in the insulating hydrocarbon solvent (b). When the colored resin particles are formed in advance by the coacervation method described in (The dispersant (A) and / or the dispersant (B) is a dispersant having a basic group (a compound having a basic group)). An oxidized polyethylene wax may be contained, and the oxidized polyethylene wax and a dispersant having a basic group may be stirred and mixed in the insulating hydrocarbon solvent (b) during production.
By using the oxidized polyethylene wax treated in the presence of the compound having a basic group, a liquid developer having excellent abrasion resistance can be obtained.

The oxidized polyethylene wax includes (i) a method of polymerizing ethylene under high pressure and high temperature using a radical catalyst, (ii) a method of polymerizing ethylene under low pressure using a Ziegler catalyst, and (iii) reducing the molecular weight of general molding polyethylene by thermal decomposition. Method, (iv) a polyethylene wax obtained by separating and purifying low molecular weight polyethylene produced as a by-product in the production of polyethylene for general molding, etc. is oxidized by an oxidation method such as air oxidation to produce a carboxyl group, Known products such as those added with a hydroxyl group, a carbonyl group, etc., or (v) a method produced by oxidizing a polyethylene for general molding can be used.

The oxidized polyethylene wax includes a dispersion and a powder. In the case of a dispersion, the insulating hydrocarbon solvent (b) is added and the dispersion contained in the dispersion is stirred. When the dispersion obtained by distilling the solvent under reduced pressure is a powder, it is preferable to use a dispersion obtained by adding the above-mentioned insulating hydrocarbon solvent (b) and stirring.

The oxidized polyethylene wax used in the present invention preferably has an acid value in the range of 0.5 to 20 mgKOH / g.
In the present invention, the acid value of the oxidized polyethylene wax is measured according to JIS K5902.
In addition, the suitable usage-amount (blending amount) of the said oxidation polyethylene wax (solid content) is the range of 0.1-10 mass% in 100 mass% of total solid content of the said liquid developer.

Further, as described above, the oxidized polyethylene wax is treated in the presence of a compound having a basic group in order to improve the electrophoretic property and improve the abrasion resistance of the printed matter obtained by printing the liquid developer. ing. As the compound having a basic group, a dispersant having a basic group can be preferably used as described in the dispersant (A) and the dispersant (B).

As the compound having a basic group, it is more preferable to use a reaction product of a polyamine compound and a hydroxycarboxylic acid self-condensate.
The polyamine compound is not particularly limited, and examples thereof include polyvinylamine polymers, polyallylamine polymers, polydiallylamine polymers, diallylamine-maleic acid copolymers, and further polyaniline units, polypyrrole units, and the like. The polymer containing is also mentioned. Examples of the polyamine compound include aliphatic polyamines such as ethylenediamine, alicyclic polyamines such as cyclopentanediamine, aromatic polyamines such as phenylenediamine, araliphatic polyamines such as xylylenediamine, hydrazine and derivatives thereof. It is done. Of these, polyallylamine-based polymers such as polyallylamine are preferable.

The hydroxycarboxylic acid constituting the hydroxycarboxylic acid self-condensate is not particularly limited. For example, glycolic acid, lactic acid, oxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxycaprylic acid, hydroxycapric acid, hydroxylauric acid, hydroxy Examples include myristic acid, hydroxypalmitic acid, hydroxystearic acid, ricinoleic acid, castor oil fatty acid, and hydrogenated products thereof. Preferably they are C12-C20 hydroxycarboxylic acid, More preferably, it is C12-C20 12-hydroxycarboxylic acid, Most preferably, it is 12-hydroxystearic acid.

Particularly preferable examples of the compound having a basic group include a reaction product of a polyamine compound and a hydroxystearic acid self-condensate, and among them, a polyamine compound and a 12-hydroxystearic acid self-condensate (polyallylamine). Reaction product of 12-hydroxystearic acid self-condensate, polyethylene polyamine and 12-hydroxystearic acid self-condensation product, reaction product of dialkylaminoalkylamine and 12-hydroxystearic acid self-condensation product, polyvinylamine And a reaction product of 12-hydroxystearic acid self-condensate and the like. Further preferred among them is a reaction product of polyallylamine and 12-hydroxystearic acid self-condensate. Examples of the commercially available products include Ajisper PB817 (manufactured by Ajinomoto Co., Inc.), Solspers 11200, 13940, 17000, 18000 (manufactured by Nippon Lubrizol).

The amine value of the reaction product of the polyamine compound and the hydroxycarboxylic acid self-condensate is preferably 5 to 300 mgKOH / g.
In the specification of the present application, the amine value means an amine value per 1 g of solid content, and a 0.1N hydrochloric acid aqueous solution is used, and potentiometric titration (for example, COMMITITE (AUTO TITRATOR COM-900, BURET B-900, TITSTATIONK) -900), manufactured by Hiranuma Sangyo Co., Ltd., and then converted into an equivalent of potassium hydroxide.

As the oxidized polyethylene wax treated in the presence of the compound having a basic group, the oxidized polyethylene wax and the compound having a basic group are stirred and mixed in the insulating hydrocarbon solvent (b) described above. From the point of improving the electrophoretic properties and further improving the abrasion resistance of the printed matter obtained by printing the liquid developer, in the insulating hydrocarbon solvent (b), the oxidized polyethylene wax is used in advance. It is preferable to use a mixture in which a compound having a basic group is stirred and mixed. Specifically, in the case of a dispersion in which the oxidized polyethylene wax is dispersed in a dispersion solvent, the insulating hydrocarbon solvent (b), a compound having a basic group is added to the dispersion of oxidized polyethylene wax. In the case of a powder, a dispersion obtained by distilling the dispersion solvent contained in the dispersion of the oxidized polyethylene wax while stirring, in the case of powder, the above insulating hydrocarbon solvent is added to the oxidized polyethylene wax of the powder. Examples of (b) a dispersion in which a compound having a basic group is added and stirred.

Next, the charge control agent to be used is one that dissolves in the insulating hydrocarbon solvent (b), and includes cobalt naphthenate, nickel naphthenate, iron naphthenate, zinc naphthenate, cobalt octylate, and octylic acid. Metallic soaps such as nickel, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate, cobalt 2-ethylhexanoate, petroleum metal sulfonate, metal salt of sulfosuccinate, Phospholipids such as lecithin, t-butyl salicylic acid metal chromium salt, t-butyl salicylic acid metal aluminum salt, t-butyl salicylic acid metal zirconium salt and other salicylic acid metal salts, polyvinylpyrrolidone resin, polyamide resin, sulfonic acid-containing resin, hydroxybenzoic acid Derivatives can be used, and among these, oxidized polyethylene Salicylic acid metal salts in view of chargeability of WAX is preferred.
In addition to the liquid developer of the present invention, other additives may be blended as necessary.

<Method for Producing Liquid Developer Obtained Using Coacervation Method>
Next, a method for producing a liquid developer obtained by using the above-described materials using the coacervation method will be described. Such a manufacturing method is an example and is not limited thereto.
Examples of the method for producing the liquid developer include the following (1) and (2).

(1) A part of pigment, dispersant (A), dispersant (B) and solvent (a) are mixed, and media type dispersers such as attritor, ball mill, sand mill, bead mill, high speed mixer, high speed homogenizer, etc. A pigment dispersion solution in which the pigment is dispersed with a non-media type disperser is obtained. Further, the binder resin and the remaining solvent (a) are added to the pigment dispersion solution, and then the insulating hydrocarbon solvent (b) is added while stirring with a high-speed shearing device to obtain a mixed solution. The pigment may be dispersed after adding a binder resin in advance.
Next, the solvent (a) is distilled off while stirring the above mixed solution with a high-speed shearing stirrer to obtain a liquid developer containing colored resin particles. In addition, when the solid content of the obtained liquid developer is high, an insulating hydrocarbon solvent (b) is added so that the required solid content concentration is obtained, and further, the charge control agent and the oxidized polyethylene wax are made basic. In the presence of a group-containing compound, an oxidized polyethylene wax dispersion dispersed in an insulating hydrocarbon solvent (b) and other additives as necessary are added to obtain the liquid developer of the present invention.
(2) Mixing part of pigment, dispersant (A), dispersant (B) and solvent (a), media type disperser such as attritor, ball mill, sand mill, bead mill, high speed mixer, high speed homogenizer, etc. A pigment dispersion solution in which the pigment is dispersed with a non-media type disperser is obtained. Furthermore, after adding a binder resin, oxidized polyethylene wax, and the remaining solvent (a) to this pigment dispersion solution, an insulating hydrocarbon solvent (b) is added while stirring with a high-speed shearing device to obtain a mixed solution. obtain. The pigment may be dispersed after adding a binder resin in advance.
Next, the solvent (a) is distilled off while stirring the above mixed solution with a high-speed shearing stirrer to obtain a liquid developer containing colored resin particles. In addition, when the solid content of the obtained liquid developer is high, an insulating hydrocarbon solvent (b) is added so that the required solid content concentration is obtained, and a charge control agent and other additives are added as necessary. A liquid developer of the present invention is obtained by adding an agent (provided that the dispersant (A) and / or the dispersant (B) is a dispersant (compound) having a basic group).

In addition, as said high-speed shear stirring apparatus, a stirring and shearing force can be applied, and a homogenizer, a homomixer, etc. can be utilized. Furthermore, there are various types such as a capacity, a rotational speed, a model, etc., and an appropriate one may be used according to the production mode. When the homogenizer is used, the rotation speed is preferably 500 rotations (rpm) or more.

In order to obtain the liquid developer of the present invention using the coacervation method, the insulating hydrocarbon solvent (b), the compound having a basic group, and polyethylene oxide in the production method described in (1) above. What was added as a dispersion containing a wax is preferable from the viewpoint of excellent migration of the oxidized polyethylene wax and improved friction resistance of the resulting printed matter.

<Liquid developer obtained using wet grinding method>
(Constituent materials)
As the pigment to be used, the same inorganic pigments and organic pigments as those described for the liquid developer obtained using the coacervation method can be used.
The content of these pigments is not particularly limited, but is preferably 2 to 20% by mass in the final liquid developer from the viewpoint of image density.

Next, as the binder resin to be used, a known binder resin (resin that does not dissolve in the solvent (b)) conventionally used in liquid developers can be used. For example, the binder resin can be obtained by using the above coacervation method. Resins similar to those described for the liquid developer to be used can be used.

Next, as a solvent used in the wet pulverization method, an insulating hydrocarbon organic solvent (solvent (b)) that does not dissolve the binder resin can be used. As this insulating hydrocarbon-based organic solvent (solvent (b)), hydrocarbons having electrical insulation properties can be used without dissolving the binder resin. Specifically, the same solvent (b) as described for the liquid developer obtained using the coacervation method can be used.

Next, as the dispersant used in the wet pulverization method, the dispersant (A) that is dissolved in the insulating hydrocarbon solvent (b) is used.
In the present invention, the indicator that the dispersant (A) is dissolved in the solvent (b) is the same as that described for the liquid developer obtained by using the coacervation method.
In addition, about the said binder resin, the meaning of "it does not melt | dissolve binder resin" is also the same.

As a specific example of the dispersant (A), the dispersant exemplified in the dispersant (A) described in the liquid developer obtained by using the coacervation method can be used.
Moreover, 2-100 mass parts is preferable with respect to 100 mass parts of colored chips of the following description, and, as for the usage-amount of the said dispersing agent (A), More preferably, it is 2-50 mass parts.

The total blending amount of the binder resin and the pigment not dissolved in the insulating hydrocarbon solvent (b) contained in the liquid developer obtained by using the wet pulverization method is preferably 10 to 50% by mass, more preferably 15 to 40% by mass. When the amount is less than 10% by mass, a high-concentration product cannot be obtained.

Next, as the oxidized polyethylene wax used in the wet pulverization method and treated in the presence of the compound having a basic group, the oxidized polyethylene wax and the basic group are mixed in the insulating hydrocarbon solvent (b). A compound in which the compound is stirred and mixed is used.
The mixture that has been stirred and mixed may be a mixture in which an oxidized polyethylene wax and a compound having a basic group are previously stirred and mixed in the insulating hydrocarbon solvent (b). In the wet pulverization method described in 1), when the colored chips are wet pulverized in the insulating hydrocarbon solvent (b) in which the dispersant having a basic group as the dispersant (A) is dissolved, the dispersant (A) Dispersant having oxidized polyethylene wax and basic group in insulating hydrocarbon solvent (b) at the time of production, containing oxidized polyethylene wax in advance in insulating hydrocarbon solvent (b) in which May be agitated and mixed.
By using the oxidized polyethylene wax treated in the presence of the compound having a basic group, a liquid developer having excellent abrasion resistance can be obtained.

As the oxidized polyethylene wax used in the wet pulverization method, the same oxidized polyethylene wax as described for the liquid developer obtained by using the above-described coacervation method can be used.
In the wet pulverization method, the amount (formulation amount) of the oxidized polyethylene wax (solid content) is in the range of 0.1 to 10% by mass in 100% by mass of the total solid content of the liquid developer.

Further, as described above, the oxidized polyethylene wax is treated in the presence of a compound having a basic group in order to improve the electrophoretic property and improve the abrasion resistance of the printed matter obtained by printing the liquid developer. ing. Preferably, a dispersant having a basic group described in the dispersant (A) can be used. As the compound having a basic group, the same compounds as those described for the liquid developer obtained using the coacervation method can be used.

As the oxidized polyethylene wax used in the wet pulverization method and treated in the presence of the compound having a basic group, the same liquid developer obtained by using the above-described coacervation method as described as a suitable example. Those are preferred.

Next, the charge control agent used in the wet pulverization method is one that dissolves in the insulating hydrocarbon solvent (b), and the charge described in the liquid developer obtained by using the coacervation method. The same control agent can be used. Of these, salicylic acid metal salts are preferred from the viewpoint of chargeability of the oxidized polyethylene wax.
In addition to the liquid developer obtained by utilizing the wet pulverization method, other additives may be blended as necessary.

<Method for Producing Liquid Developer Obtained Using Wet Grinding Method>
Next, a method for producing a liquid developer obtained by using a wet pulverization method using the above materials will be described. Such a manufacturing method is an example and is not limited thereto.
Examples of the method for producing a liquid developer by the wet pulverization method include the following (1) and (2).

(1) The pigment and binder resin are heated and kneaded (three rolls, twin screw extruder, etc.), and after cooling, the obtained colored chips are dry pulverized using a dry pulverizer (grand pulverization obtained by dry pulverization) The product preferably has an average particle size of 7 to 12 μm). When the kneaded material to be dry-pulverized is soft, for example, when the softening point is 100 ° C. or lower, it is cooled and embrittled with liquid nitrogen or solid carbon dioxide and pulverized. Next, using a wet pulverizer, the ground pulverized product obtained by the dry pulverization is wet pulverized in an insulating hydrocarbon solvent (b) in which the dispersant (A) is dissolved to obtain a wet pulverized product. Furthermore, the oxidized polyethylene wax dispersion in which the oxidized polyethylene wax is dispersed in the insulating hydrocarbon solvent (b) in the presence of the compound having a basic group in the wet pulverized product, the charge control agent, and other if necessary Additives are added to obtain the liquid developer of the present invention. The charge control agent is added after wet pulverization, but can also be added during wet pulverization.
(2) Insulating hydrocarbon in which a pulverized product obtained by dry pulverization as in the above (1) is dissolved in a dispersant having a basic group as the dispersant (A) and dispersed with oxidized polyethylene wax A wet pulverized product is obtained by wet pulverization in the solvent (b) of the system. Furthermore, a charge control agent and other additives as required are added to the wet pulverized product to obtain the liquid developer of the present invention. The charge control agent is added after wet pulverization, but can also be added during wet pulverization.

As the dry pulverizer, for example, a hammer mill, a jet mill, a pin mill, a turbo mill, a cutter mill, a ball mill and the like can be used as appropriate.
Examples of the wet pulverizer include media type dispersers such as Eiger mill, attritor, sand mill, dyno mill, ball mill, DCP mill, apex mill, pearl mill, Ultimizer (manufactured by Sugino Machine Co., Ltd.), Nanomizer (Nanomizer). Medialess pulverizers such as Microfull Dizer (manufactured by Mizuha Kogyo Co., Ltd.), DeBee 2000 (manufactured by DeBee), and the like can be used as appropriate. The toner particles in the liquid developer obtained by wet pulverization preferably have an average particle diameter of 0.1 to 5 μm, more preferably 0.1 to 3 μm from the viewpoint of obtaining a high-definition image.

In order to obtain the liquid developer of the present invention using the wet pulverization method, in the production method described in the above (1), the oxidized polyethylene wax has an insulating hydrocarbon solvent (b) and a basic group. What was added as a dispersion containing a compound and an oxidized polyethylene wax is preferred because the oxidized polyethylene wax has excellent migration properties and the resulting printed matter has improved friction resistance.

Since the liquid developer of the present invention has the above-described configuration, it has excellent wear resistance. In addition, the chargeability and electrophoretic properties are also good.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “%” means “mass%” and “part” means “part by mass”.

Pigment, dispersant (A), dispersant (B), compound having a basic group, binder resin, wax, charge control agent, solvent (a), insulating hydrocarbon solvent used in Examples and Comparative Examples (B) is as follows.
<Pigment>
MA285 (Mitsubishi Chemical Corporation carbon black)
<Dispersant (A)>
Ajisper PB817 (manufactured by Ajinomoto Co., Inc., a dispersant having a basic group)
The solubility of the dispersant (A) in THF (solvent (a)) was 1.0 g / 100 g or more.
The solubility of the dispersant (A) in Moresco White P-40 (solvent (b)) was 1.0 g / 100 g or more.
<Dispersant (B)>
In a four-necked flask equipped with a reflux condenser, a nitrogen gas inlet tube, a stirrer, and a thermometer, 132.6 parts of a toluene solution of a polycarbodiimide compound having a carbodiimide equivalent of 316 having an isocyanate group (solid content 50%), N- 12.8 parts of methyldiethanolamine was charged and maintained at about 100 ° C. for 3 hours to react an isocyanate group with a hydroxyl group. Next, 169.3 parts of a ring-opened product of polycaprolactone having a carboxyl group at the terminal and having a number average molecular weight of 2000 were charged and held at about 80 ° C. for 2 hours to react the carbodiimide group and the carboxyl group, and then under reduced pressure. The toluene was distilled off to obtain a pigment dispersant (dispersant having a solid content of 100% and a basic group).
The solubility of the dispersant (B) in THF (solvent (a)) was 1.0 g / 100 g or more.
The solubility of the dispersant (B) in Moresco White P-40 (solvent (b)) was less than 0.01 g / 100 g (measurement limit value).
<Compound having a basic group>
Azisper PB817 (Ajinomoto Co., Inc., reaction product of polyallylamine and 12-hydroxystearic acid self-condensate, amine value 15 mgKOH / g)
<Binder resin>
YD-011 (epoxy resin / manufactured by Toto Kasei)
<Wax>
Oxidized polyethylene wax (acid value 10 mgKOH / g, average particle size 14 μm, solid content 10%)
Oxidized polyethylene wax (acid value 1 mgKOH / g, average particle size 20 μm, solid content 10%%)
Polyethylene wax (PA60, manufactured by Polycon, solid content 26%)
Paraffin wax (Amicus 1204, Honeywell, solid content 100%)
<Charge control agent>
t-Butylsalicylic acid metal chromium salt <solvent (a)>
Tetrahydrofuran (THF) (SP value 9.1)
<Insulating hydrocarbon solvent (b)>
Moresco White P-40 (Matsumura Petrochemical Laboratory, SP value less than 8.5)

(Wax dispersion)
Wax dispersion 1
200 parts by mass of oxidized polyethylene wax having an acid value of 10 mg KOH / g, 2 parts by mass of Azisper PB817 dispersion as a compound having a basic group, and 78 parts by mass of Moresco White P-40 are mixed and contained in the oxidized polyethylene wax while stirring. The dispersion solvent obtained was distilled under reduced pressure to obtain a wax dispersion 1.

Wax dispersion 2
200 parts by mass of oxidized polyethylene wax having an acid value of 10 mgKOH / g and 80 parts by mass of Moresco White P-40 were mixed, and the dispersion solvent contained in the oxidized polyethylene wax was distilled under reduced pressure to obtain wax dispersion 2. .

Wax dispersion 3
200 parts by mass of oxidized polyethylene wax having an acid value of 1 mg KOH / g, 2 parts by mass of Ajisper PB817 dispersion as a compound having a basic group, and 78 parts by mass of Moresco White P-40 are mixed and contained in the oxidized polyethylene wax while stirring. The dispersion solvent obtained was distilled under reduced pressure to obtain wax dispersion 3.

Wax dispersion 4
77 parts by mass of polyethylene wax and 80 parts by mass of Moresco White P-40 were mixed, and the dispersion solvent contained in the polyethylene wax was distilled under reduced pressure while stirring to obtain a wax dispersion 4.

Wax dispersion 5
20 parts by mass of paraffin wax and 80 parts by mass of Moresco White P-40 were mixed, and the dispersion solvent contained in the paraffin wax was distilled under reduced pressure to obtain a wax dispersion 5.

(Liquid developer containing colored resin particles obtained using the coacervation method)
20.0 parts of MA285, 8.0 parts of dispersing agent (B) and 72.0 parts of THF were mixed, kneaded for 15 minutes with a paint shaker using 5 mm diameter steel beads, and then using 0.05 mm diameter zirconia beads. The mixture was further kneaded for 2 hours with an Eiger motor mill M-250 (manufactured by Eiger Japan). To 17.5 parts of this kneaded product, 21 parts of binder resin and 61.5 parts of THF were added, and the mixture was heated and stirred at 50 ° C. Thereafter, 1.0 part of dispersant (A) was added and stirred, and then stirred while diluting with 73.1 parts of Moresco White P-40 (manufactured by Matsumura Petrochemical Laboratories) to obtain a mixed solution. Next, using a device in which a solvent evaporating device (connected to a decompression device) is connected to a homogenizer consisting of a closed stirring tank, the temperature of the mixture is adjusted by the decompression device while stirring the mixture at high speed (revolution: 5,000 rpm). The pressure was reduced to 50 ° C., and THF was completely distilled off from the sealed stirring tank to obtain a liquid developer (solid content: 26.9% by mass).

(Liquid developers obtained using the coacervation methods of Examples 1 to 4 and Comparative Examples 1 to 3)
In the liquid developer containing the colored resin particles obtained by using the coacervation method, the wax dispersions 1 to 5 and the charge control agent are blended so as to have the composition shown in Table 1, and Examples 1 to 4 are mixed. And the liquid developer of Comparative Examples 1-3 was obtained.

(Liquid developer containing colored resin particles obtained by wet pulverization method)
After cooling the kneaded meat (colored chip) obtained by melting and kneading 250 parts of MA285 and 750 parts of binder resin at 140 ° C. using three hot rolls, a jet mill (Nippon Pneumatic Co., Ltd.) ). Next, 140 parts of this pulverized product, 8.8 parts of dispersant (A), 551.2 parts of Moresco White P-40 (manufactured by Matsumura Petrochemical Laboratory) as the insulating hydrocarbon solvent (b) Was wet-ground for about 90 minutes at a temperature of 40 ° C. using an Eiger mill (trade name M-250) filled with zirconia beads having a diameter of 0.5 mm to obtain a liquid developer (solid content: 21.3 mass%). The average particle diameter of the obtained colored resin particles was 1 to 2 μm (optical microscope (measured visually by Olympus Corporation)).

(Liquid developers obtained using the wet pulverization methods of Examples 5 to 6 and Comparative Example 4)
In the liquid developer containing the colored resin particles obtained using the wet pulverization method, a wax dispersion 1-2 and a charge control agent are blended so as to have the composition shown in Table 1, Examples 5-6, A liquid developer of Comparative Example 4 was obtained.

<Performance evaluation>
The charging property, migration property, and friction resistance were evaluated by the following evaluation methods. The results are shown in Table 1.
(Chargeability and migration)
About 99 parts of the wax dispersions 1 to 5, 1 part of the charge control agent was added and stirred, and the wax particles were observed using an electrophoresis cell (condition: interelectrode distance: 80 μm, applied voltage: 20 V).
(1) Electrophoretic ◯: Wax particles migrate smoothly without agglomeration Δ: Wax particles migrate while forming aggregates ×: Wax particles agglomerate between electrodes and do not move (2) Chargeable migration cell When voltage is applied to
+: −90% or more of wax particles migrate to the electrode side −: + 90% or more of wax particles migrate to the electrode side ±: Other than the above

(Abrasion resistance test)
Each liquid developer is supplied between the rollers, then an applied voltage is applied, and the particles in the liquid developer are electrophoresed. Then, the liquid developer on the roll on the electrode side is transferred to paper, and the oven at 140 ° C. After drying for 10 seconds, a friction test was performed with a vibration-type friction tester (500 g, 10 times).
○: No scratch on the printed surface Δ: Peel off if less than 10% of the area subjected to the friction test ×: Peel off if not less than 10% of the area subjected to the friction test

From Table 1, the friction resistance of the liquid developer of the Example using the oxidized polyethylene wax treated in the presence of the compound having a basic group had no problem in practicality. On the other hand, in the comparative example using no wax or polyethylene wax or paraffin wax, the friction resistance was inferior. In addition, the migration property and charging property of the oxidized polyethylene wax dispersion had no problem in practical use, whereas the properties of the polyethylene wax dispersion and paraffin wax were inferior.

The liquid developer of the present invention is suitably used for printing machines, copying machines, printers, facsimiles and the like.

Claims (7)

Colored resin particles composed of at least two components of a pigment and a binder resin, an insulating hydrocarbon organic solvent (solvent (b)) that does not dissolve the binder resin, and a dispersant (dispersant (A) that dissolves in the solvent (b) And a liquid developer comprising an oxidized polyethylene wax treated in the presence of a compound having a basic group, and a charge control agent. Colored resin particles comprising at least three components of pigment, solvent (b) insoluble or sparingly soluble dispersant (dispersant (B)) and binder resin, solvent (b), dispersant (A), and charge control agent In a liquid developer obtained using the coacervation method,
The liquid developer according to claim 1, further comprising an oxidized polyethylene wax dispersion in which oxidized polyethylene wax is dispersed in a solvent (b) in the presence of a compound having a basic group. In a liquid developer containing a colored resin particle composed of at least two components of a pigment and a binder resin, a solvent (b), a dispersant (A), and a charge control agent, and obtained by using a wet pulverization method,
The liquid developer according to claim 1, further comprising an oxidized polyethylene wax dispersion in which oxidized polyethylene wax is dispersed in a solvent (b) in the presence of a compound having a basic group. Pigment, binder resin, solvent for dissolving the binder resin (solvent (a)), solvent (b) that does not dissolve the binder resin and has a lower SP value than the solvent (a), the solvent (a), and Dispersing agent (A) that dissolves in both (b), dispersing agent (B) that dissolves in solvent (a) and is insoluble or sparingly soluble in solvent (b), and oxidized polyethylene wax From the mixture, the solvent (a) is distilled off, and the charge is controlled in a dispersion obtained by using a coacervation method in which the binder resin and the dispersant (B) that are in a dissolved state are precipitated. A liquid developer containing an agent,
The liquid developer according to claim 1, wherein the dispersant (A) and / or (B) is a dispersant having a basic group. A colored chip obtained by heating and kneading a pigment and a binder resin is dispersed in a mixture containing a dispersant having a basic group as a dispersant (A), an oxidized polyethylene wax and a solvent (b), and a wet pulverization method The liquid developer according to claim 1, wherein a charge control agent is blended in a dispersion obtained by utilizing the above. 4. The liquid developer according to claim 1, wherein the compound having a basic group is a reaction product of a polyamine compound and a 12-hydroxystearic acid self-condensate. The liquid developer according to claim 1, wherein the charge control agent is a salicylic acid metal salt.